In the field of electric power industry, aluminum electric wires, which include conductor wires made from aluminum-based materials that are light in weight and excellent in electrical conductivity, are conventionally used as overhead power lines. Meanwhile, in the field of automobile industry, copper electric wires, which include conductor wires made from copper-based materials that are excellent in electrical conductivity and in cost efficiency, are conventionally used as signal lines and electric power lines.
In these years, electric vehicles and fuel-cell vehicles that can put a reduced burden on the environment have been developed actively in the field of automobile industry. In these kinds of vehicles, electric power lines larger in diameter than conventional signal lines should be used as electric wires connected to batteries and fuel cells because large amounts of electric power need to be transmitted from the batteries and the fuel cells.
Meanwhile, a move to improve fuel efficiency by reducing the weight of automotive vehicles has been accelerated in the field of automobile industry, so that even the total weight of electric wires used in one automotive vehicle cannot be overlooked, and weight reduction of the electric wires is also desired.
Thus, aluminum electric wires, which include conductor wires made from aluminum having a specific gravity (2.70 g/cm3) that is about one third of copper (8.96 g/cm3), have been more often used in automobiles in order to reduce the total weight of electric wires.
Conventionally, connecting terminals arranged to connect electric wires with each other, or connect electric wires with terminals of external electronic appliances are used in routing any kinds of electric wires, i.e., not exclusively to routing aluminum electric wires. Most of the connecting terminals are made from copper-based materials from the viewpoints of electrical conductivity and cost efficiency.
The connecting terminals made from copper-based materials are often used also in routing aluminum electric wires in automotive vehicles, so that crimped terminal portions where the connecting terminals are crimped onto the aluminum electric wires define bimetal contact portions. For example, in using connecting terminals made from copper, the difference between the normal electrode potential of copper, which is +0.34 V, and the normal electrode potential of aluminum, which is −1.66 V, becomes 2.00 V, which is large. In addition, in using connecting terminals made from copper that are coated with tin plating, the difference between the normal electrode potential of tin, which is −0.14 V, and the normal electrode potential of aluminum becomes 1.52 V. Thus, if the crimped terminal portions are exposed to water while the vehicles are moving in the rain or washed, or because of condensation, and an electrolyte solution such as rain water enters to stay in the crimped terminal portions, the three members of aluminum, copper and electrolyte solution, or the three members of aluminum, tin and electrolyte solution form batteries, so that bimetallic corrosion builds up in the aluminum conductors that function as positive electrodes of the batteries.
When ionization of the aluminum electric wires, which are electrically base, proceed to promote the corrosion as described above, the contact states of the crimped terminal portions become worse, which could make the electrical characteristics of the crimped terminal portions unstable, could increase contact resistance, could increase electrical resistance because of the reduced wire diameters, and could break the electric wires. Consequently, the electrical components could malfunction, or could break down.
PTL 1 discloses, in order to prevent corrosion from building up in an aluminum electric wire having the configuration described above, a manner for preventing a factor (corrosion factor) such as water and oxygen that causes the corrosion from entering in a bimetal contact portion by coating a portion where an aluminum conductor wire is exposed in a crimped terminal portion with an anticorrosive resin.